(1) Field of the Invention
This invention relates to a guidance system for agricultural tractors and more particularly to that part of the system which senses the path along the land which the tractor is to follow. Farmers raising row crops are those having ordinary skill in the art.
(2) Description of the Related Art
Tractor guidance systems have been developed over a long period of time. This development shows that generally there are three elements to a guidance system for a tractor. These might be broken down to (1) path sensors; (2) deviation detectors which measure the deviation as sensed by the sensor; and (3) steering means to guide the tractor responsive to the detected deviation.
This particular patent application relates to the path sensor.
As used in this application, "path" means the line or row on the land that the tractor is to follow. "Path" might also be considered a track or trail or a course that the tractor is to follow. At all times, "path" as used in this application, will mean a course on the land having at least one structural guide which may be mechanically sensed. Often the guide will be a furrow. At other times the guide will be a row of stalks. Other times, the guide might be the bed between furrows.
When this structural guide is a furrow; the furrow can be mechanically sensed by a furrow follower.
When a bed is the structural guide; the bed might be followed by a structure similar to, but opposite to a furrow follower.
The guide might be a row of stalks. This is often the case when the agricultural operation is cultivation of an established crop having stalks with sufficient structural strength to withstand feelers against them. Of most importance, when harvesting cotton, it is desirable for the harvester to follow the row of stalks as exactly as possible.
The following U.S. patents show examples of path sensors:
______________________________________ KNIGHT 1,868,360 ROBERSON ET AL 3,402,784 CLEVELAND 3,611,286 BRUM 4,366,756 FASSE 4,406,232 BECK 4,607,716 STIFF ET AL 4,367,802 COLLAGAN ET AL 4,180,133 ______________________________________
KNIGHT, illustrates a row follower having a sensor as shown by the numeral 8 in that patent.
ROBERSON has a furrow follower illustrated by the numeral 25 or 26.
CLEVELAND, discloses a spherical shape or ball 44 supported by a helical spring 38 used as a furrow follower.
BRUM, discloses a furrow follower in the form of a wheel or disk 4.
FASSE, discloses a furrow follower or a pair of furrow followers such as 24 and 54. Also, FASSE et al, discloses and seeks correction for one of the problems encountered, that is, the problem of obstruction or a discontinuity of the path represented by a pile of dirt 57 within the path. The result of the problem encountered by FASSE is called herein "bounce". It might be considered a recoil or an elastic movement or a kick. However, it is to be understood that the bounce is not limited to a vertical direction. Particularly when different types of row followers are being used and a wider furrow than a sharply defined V-furrow as shown by FASSE is present, the bounce might be lateral. FASSE's solution to this problem is to provide two drags so that one is always in the furrow.
BECK, discloses a shoe-like furrow follower 56. The BECK disclosure is particularly instructive in showing a furrow which has a flat bottom. The bottom in FIG. 2 of the BECK drawings which of course presents a path more difficult in following than a sharply defined V-shaped furrow as illustrated in FASSE or CLEVELAND.
STIFF et al, discloses two co-axial disks separated apart to follow a furrow.
COLLAGAN et al, discloses a non-spherical ball-like furrow follower.
The design of row followers would not be particularly difficult if all of the paths were uniform. I.e., if the furrows were V-shaped without irregularities or weeds or clods of dirt therein, and the tractor was traveling slowly, many different row followers would be satisfactory. Likewise if the stalks of a row of crop were closely spaced, and in good alignment without irregularities, there would be no problem in having a "wand" or other feeler to follow the crop row. However, it is often desirable to travel at higher speeds, and there are clods in furrows, as well as sometimes clods along side a row of crop. The stalks often have skips or gaps therein and also irregularly spaced stalks or weeds to one side which deflect or "bounce" the sensor.